A plastic lens is lighter in mass and superior in moldability, processability, dye-affinity and the like as well as being less likely to break to provide superior safety as compared to a glass lens, so that the plastic lens has been rapidly becoming popular in an eye-glass field and accounts for largest share. In addition, there have been developed high-index materials such as a thiourethane resin and an episulfide resin in response to demands for thinner and lighter lenses. Meanwhile, since the plastic lens more likely gets scratches than the glass lens, a hard coat layer is typically formed on a surface of the plastic lens to enhance its surface hardness. In addition, an antireflection film is formed by vapor-depositing an inorganic substance on an upper surface of the hard coat layer in order to prevent surface reflection, and a stainproof layer formed of a fluorine-containing organosilicon compound is formed on an upper surface of the antireflection film in order to enhance water/oil repellency of the surface of the antireflection film. As described above, the plastic lens has been being improved as a high-performance lens owing to technological innovation of surface treatment.
However, the plastic lens has a drawback with its low thermal resistance. Furthermore, due to use of a resin material with higher refractive index for the plastic lens, the thermal resistance of the plastic lens tends to be degraded Especially, the inorganic antireflection film in surface coating layers cannot follow thermal expansion deformation of the plastic lens as a base material, resulting in causing cloud or cracks, and this drawback is more significant in a plastic lens with higher refractive index.
Since the inorganic antireflection film is formed by vacuum deposition, the inorganic antireflection film typically has high film density and has a performance for blocking factors that degrades durability of the plastic lens (e.g., oxygen, moisture, ultraviolet light, etc.) from contacting the hard coat layer as a lower layer from outside of the lens, namely the inorganic antireflection film has a protection effect. With such inorganic antireflection film, even when the hard coat layer as the lower layer is formed using a coating composition containing as the main component a titanium oxide having an anatase type crystalline structure that has low light resistance, the durability of the plastic lens can be ensured to some extent. On the other hand, since the antireflection film formed of an organic film has relatively lower film density than the inorganic antireflection film, which has a structure with voids, the protection effect as that of the inorganic antireflection film cannot be provided. Accordingly, when the hard coat layer is formed using the coating composition containing as a main component the titanium oxide having the anatase type crystalline structure, the durability of the plastic lens is not sufficient, so that the hard coat layer as the lower layer requires higher durability.
In order to satisfy such requirement, there has been proposed a technology to form a hard coat layer using a coating composition containing fine metal oxide particles that contain as a main component a titanium oxide having a rutile type crystalline structure (see, for instance, Document 1: JP-A-11-310755). Since the hard coat layer uses the titanium oxide with low photoactivation effect, it can realize enhanced durability and higher refractive index as compared to the related-art titanium oxide with the anatase type crystalline structure.
Further, since the antireflection film formed of the organic film has relatively lower film density than the inorganic antireflection film as described above and has a structure with voids, scratch resistance and chemical resistance thereof are not sufficient.
In order to solve such problem, there have been proposed: a method for co-hydrolyzing a perfluoroalkylethyl group-containing silane and various silane compounds such as a tetraalkoxysilane (see, for instance Document 2: JP-A-2002-53805); a system that is obtained by mixing and co-hydrolyzing a perfluoroalkyl group-containing silane, a disilane compound containing perfluoroalkylene as a spacer and a tetraalkoxysilane (see, for instance, Document 3: JP-B-6-29332); and a system that is obtained by mixing and co-hydrolyzing a perfluoroalkyl group-containing silane, a disilane compound containing a perfluoroalkylene as a spacer and an epoxy-functional silane (see, for instance, Document 4: Japanese Patent No. 2629813), which have succeeded in ensuring relatively proper stain resistance, scratch resistance, adherence and antireflection property.
Also, there has been known a composition that contains a disilane compound having a specific structure or its (partial) hydrolysate and realizes higher chemical resistance than related arts (see, for instance, JP-A-2004-315712).
However, when a related-art antireflection film formed of the organic film is formed on an upper surface of the hard coat layer containing the titanium oxide of the rutile type like an arrangement disclosed in Document 1, the durability of the hard coat layer and the scratch resistance, chemical resistance and thermal resistance of the organic antireflection film are not sufficient, thereby requiring further improvements of performances.
As for each of the compositions disclosed in Documents 2 to 4, the fluorine content is reduced. Accordingly, chemical resistance against chemical agents such as a household detergent, especially alkali resistance which is a weak point of polysiloxane system, is not sufficient, though such chemical resistance had been essentially proper in related arts. Thus, there is still a problem in practical use.
As for the composition disclosed in Document 5, when high heat is applied in a film forming process or other processes or when high heat is applied after the film forming process, cracks are likely generated. Especially, when a film is formed on a base material with plasticity such as a plastic, many cracks are generated
Meanwhile, a thiourethane resin and an episulfide resin, which have been a mainstream of materials used for a plastic lens base material with high refractive index, each have a sulfur atom as a backbone. The sulfur atom hardly interacts with a polar group such as a silanol group in the organosilicon compound contained in the hard coat layer and is known to have a property to impede hardening of the hard coat layer itself, thus impeding adherence between the hard coat layer and the plastic lens base material. Especially, when the antireflection film formed of the organic film is formed on the upper surface of the hard coat layer, the adherence between the hard coat layer and the plastic lens base material is not sufficient, and in addition, moisture and oxygen having passed through the organic film degrade the hard coat layer. Thus, with the arrangement in which the antireflection film formed of the organic film is formed on the upper surface of the hard coat layer, it has been difficult to achieve sufficient durability (adherence and protection effect).
There is much demand for a tinted lens as a plastic lens for eye-glasses, and the plastic lens base material is often tinted with a disperse dye. In such case, since a dye exists on a surface of the plastic lens base material, the adherence between the hard coat layer and the plastic lens base material becomes lower as compared to non-tinted lenses. It has been found out that the disperse dye existing on the surface of the plastic lens base material is deteriorated by the ultraviolet ray and oxygen. Especially, when the antireflection film formed of the organic film is formed on the upper surface of the hard coat layer, this deterioration becomes significant, resulting in degrading the adherence between the hard coat layer and the plastic lens base material.
An object of the invention is therefore to provide, as an optical component having an antireflection film formed of an organic film, a plastic lens with enhanced durability of an antireflection film and a hard coat layer as well as a manufacturing method of the plastic lens.